Locking system responsive to an electronic key

ABSTRACT

A locking system comprises locking means locking, for example, a drawer, an inductive pick-up and means for responding to an output from the pick-up to release the locking means, and a key device having an inductive field generator which can produce an output in the pick-up by induction at close range. The sensing system can be tuned to respond only to a key device generating one or more particular frequencies and a lockout arrangement can be provided to prevent release if any other frequency is present.

United States Patent [191 [111 3,829,836 Clarke Aug. 13, 1974 1 LOCKINGSYSTEM RESPONSIVE TO AN ELECTRONTC KEY Inventor: Walter Wilson HughClarke, Marsh Ln., Eversley, Hampshire, England Filed: Oct. 13,1972

Appl. No.: 297,303

US. Cl 340/171 R, 340/171 PF Int. Cl H04q 9/10, H04q 9/12 Field ofSearch 340/171 R, 171 PF References Cited UNITED STATES PATENTS 9/1969Levine 340/171 R l/l970 Clark 340/171 R 11/1970 Parisoe 340/171 X 2/1971Flook 340/171 PF Primary ExaminerHarold l. Pitts Attorney, Agent, orFirm-Lerner, David, Littenberg & Samuel [57] ABSTRACT A locking systemcomprises locking means locking, for example, a drawer, an inductivepick-up and means for responding to an output from the pick-up torelease the locking means, and a key device having an inductive fieldgenerator which can produce an output in the pick-up by induction atclose range. The sensing system can be tuned to respond only to a keydevice generating one or more particular frequencies and a lockoutarrangement can be provided to prevent release if any other frequency ispresent.

9 Claims, 5 Drawing Figures PMENTEDAUG 1 3 I974 sum am 5 Q RN R QDO -LOCKING SYSTEM RESPONSIVE TO AN ELECTRONIC KEY Y FIELD OF THE INVENTIONBACKGROUND OF THE INVENTION US. Pat. No. 3,564,501 discloses a systemfor unlocking a door, in which an appropriate radio transmitter iscarried by the authorised person. When the door knob is slightly turnedreceiver circuitry is suddenly actuated to check whether the frequencyof the transmitter is the correct one. If not, a lockout channel ensuresthat further turning of the door knob, and hence open- I ing of thedoor, is prevented. At the time when the circuitry is actuated thetransmitter may be very close, since it is on the person. The systemmust therefore be arranged so that at very short range the receiveramplifiers will not become saturated because this could allow the tripor release channel to operate before the lockout channel if ahigh-powered broad band transmission were applied to the systemby anunauthorised person. On the other hand, the signal strength can easilythen be insufficient to operate the trip or release channel if thetransmitter carried by an authorisedperson is a little further away.Thus for satisfactory operation the transmitter would always have to bepositioned rather precisely or relatively expensive automatic volumecontrol circuitry would have to be built into thereceiver.

Furthermore, the power of small radio transmitters in relation to theircost is relatively low, and at low powers considerable signalamplification in the receiver will be needed to operate a lockingdevice, so that to obtain the necessary output power it is necessary tohave either a relatively high-powered transmitter of several stages ofamplification in the receiver, either of which involves consequentexpense.

SUMMARY OF THE INVENTION An object of this invention is to provide alocking system which at least partly overcomes the disadvantages of sucha prior system.

This invention provides a system in which a key device comprises aninductive field generator and the sensing system becomes inductivelycoupled to the generator by the generated field, at sufficiently shortThus the generating and sensing circuitry can be very simple andinexpensive.

The sensing system is actuated as soon as the coupling reaches athreshold level as the key device approaches a pick-up device. Thecircuitry thus takes its own decision when the signals in it are at asuitable level, and is not suddenly loaded with input signals by theoperation of a door-knob, so that the complication and expense ofautomatic voltage control is not required while at the same time precisepositioning of the key device is unnecessary.

The key device may remain small enough to be worn inthe manner of awristwatch.

In order that the invention may be more clearly understood, embodimentsthereof will now be described, by way of example, with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic diagram of alocking system in accordance with the invention,

FIG. 2 shows two-channel sensing circuitry for use in the invention, inblock diagram form,

FIG. 3 shows qualitatively the frequency characteris tics of right andwrong inductive field generators,

FIG. 4 shows qualitatively the frequency response of the narrow and wideband subchannels of the sensing circuitry of FIG. 2, and

FIG. 5 shows qualitatively the outputs from the two subchannels whenradiation from a wrong and a right generator is applied to the sensingcircuitry of FIG. 2.

' DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 1 illustrates a lockingsystem, by means of which energisation of a solenoid, when desired, iseffected. The solenoid may be so arranged that when energised itwithdraws a latching member which locks, for example, a desk drawer in aclosed position, this being known in itself.

A DC power supply unit 15 has its input connected to the AC mains andhas its output lines 16 connected on the one hand to the power supplyinput of amplifier and detector circuitry 17 and on the other hand, vialines 18, to input terminals of the solenoid 9. The contacts 19 of arelay whose coil 20 is fed from the output of the amplifier and detectorcircuitry 17 are connected in one of the lines 18 so that when the coil20 is energised the contacts 19 will be closed and the solenoid 9 willbecome energised from the supply unit 15.

The actual circuitry of the DC power supply unit 15 and the amplifierand detector circuitry 17 may be of any suitable kind, various suitablecircuitry being known. The output from the DC power supply unit 15 maybe, for example, about 12 volts.

Connected to the input of the amplifier and detector circuitry 17 is apick-up 21 consisting of an inductive coupling element in theform of aferrite core 22 carrying a coil 23.

The key device for the system is a self-contained inductive fieldgenerator 24 which, as already mentioned,

may consist of a battery driven transistor oscillator,

which may be allowed to run permanently, driving an inductive couplingelement in the form of a coil on a ferrite core.

The pick-up 21' will be positioned, somewhere in. the desk, orelsewhere, so that the -key device 24 can be brought into its vicinity.When the key device approaches the pick-up and the distance X betweenthe device 24 andpick-up 21 becomes sufficiently small that the signalinduced in the pick-up 21 is great enough to produce an output from theamplifier and detector circuitry 17 which is effective to close thecontacts 19, the solenoid 9 will be energised, thereby releasing thelocking device in the manner already referred to.

' It will be appreciated that the amplifier and detector circuitry 17produces a DC output voltage from the oscillatory input voltage which itreceives from the pickup 21. i

By virtue of'the nature of electromagnetic relays they release at alower current than is required to operate them. Thus an extended rangebetween the key and the pick-up may occur without re-locking, once theyhave been close enough together to operate the relay. For example,closure can occur at 40 centimetres and re- Opening at 60 centimetresrange. This effect can also be enhanced by adding a biassing signal tothe rectified DC signal from the detector.

An automatic closing means may also be incorporated. For example, it ispossible to connect a small motor to the back of the'drawer by a cordwrapped on a small diameter pulley driven by the motor and havechangeover contacts on the relay to ensure'that the motor is energisedwhen thelocking device is not..The motor will then wind up the cord andre-close the drawer if it has been left open, once the key device is outof the vicinity of the pick-up. To protect the motor from continuousstall load'a microswitch within the drawer can be set to interrupt thesupply to the motor once the draweris closed. An alternativeclosingarrangement may comprise a pin for holding the drawer openagainst a bias spring, the pin being withdrawn by a=solenoid operatedbythe changeover-contacts, thus allowing-the drawer to be closed by thespring.

From the security point of view, the person responsible for a'desk,cabinet or till, for example, merely has to close the drawer to ensurelocking, and since unlocking will occur jautomatically once hereturns'(provi ded the key de'viceis on'his person and the rangeproperlyadjusted) there is little, ifan'y, incentive for him to not close andthus lock the drawer to avoid the normal trouble of unlocking it later.Of course, thesystem is even more secure if the automatic closingarrangement described above is also incorporated. The operating range ofthe system will normally be adjusted such that which may be of the samekindas described above. The

output signal from the pick-up 101 is passed by an isolator stage 102 tothe input of a first channel generally indicated at 103 and cated at-104.

The channel 103 comprises two subchannels, firstly a narrow frequencyband subchannel which includes a narrow band amplifier, 105 receivingthe output from a second channel generally indithe isolator stage 102and applying its output signal to f a lock-in relay 106, and' secondly,a wide band ampli- The application of a sufficient input signal .torelay 108'operates contacts 112 which are effective, as will be morefully described, to inhibit operation of the relay 106, therebypreventing any signals passing through the narrow band subchannel fromresulting in operation of the supply circuit contacts 110.

,the desk or cabinet is unlocked only when the person responsible isclose enough to supervise it and once he The second channel 104 is thesame as the first channel 103 withthe' exception that the frequency bandof band characteristic of these amplifiers, as compared with capacitivecouplings 114, 114'at the corresponding positions in the wide bandamplifiers 107, 107'. The effect of the capacitors is to cut off the lowend of the frequency response curve of the wide band amplifiers so as toexclude the possible effect of stray mains frequency. Each of theamplifiers 105, 107, 105' and 107 preferably incorporates an adjustablepotentiometer (not shown) by which the gains of these amplifiers canrespectively be adjusted.

. To simplify explanation of the operation of the sensing circuitry ,it'will be' assumed that it has only one channel, namely the channel 103,and that only the pair of contacts 110 lies in the power supply circuit111 of the solenoid. The effect of the inclusion of a second and furtherchannels will then be explained.

Assume that an inductive field generator having a relatively welldefined frequency corresponding to that of the narrow band amplifier 105is brought within rangeof the inductive pick-up 101. The output signalof such a generator, or'key device, is'indicated by the curve A" in FIG.3. Such a generator would be the right key for a locking system tuned tothat frequency.

Because of the coincidence of frequencies the narrow band amplifier 105will produce arelatively high amplitude output signal as indicated at121' in H6. 5 while, byvirtue of suitable setting or adjustment of therelative gains of amplifiers 105 and 107, the wide band amplifier 107will produce a lower output signal as indicated at 122 in FIG. 5. Thus,as the generator approaches the pick-up the inductive coupling willbecome great enough for the relay 106 to be operated, whose'input signalis the greater, and hence the wide bandsubchannel will be immediatelyrendered inefiective by closure of contacts 109 and the power supplycircuit will be energised by closure of contacts 110 so that thesolenoid'9 will operate system.

to release thelocking Assume now that awrong frequency generator, i.e.one whose frequency is not within the band of the narrow band amplifier105 in the sensing circuitry, is brought towards pick-up 101, thegenerator field being indicated by the broken line B in FIG. 3. Becausethe frequency is well within the range of the wide band amplifier 107this amplifier will produce the same amplitude of output signal asbefore, as indicated at 122' in FIG. 5. However, only very small outputsignals will be obtained from amplifier 105 as indicated at 121' in FIG.5, the small amplitude of this signal depending on the degree of overlapbetween the frequency spread of the generator and the pass band of thenarrow band amplifier 105. In these circumstances, it will be evidentthat relay 108 in the wide band subchannel will be operated first toclose contacts 112 thus locking out or inhibiting the action of relay106 in the narrow band subchannel and preventing the contacts 110 frombeing closed to release the locking system.

If an attempt were made to deceive the system by bringing a widefrequency band generator close to the pick-up 101, then, assuming thatits total power is only about the same as that of the narrow bandgenerator previously considered, the output from the wide bandsubchannel would still be at about the level 122 or 122' whereas, sinceonly a small proportion of its output would be within the pass band ofthe narrow band amplifier 105, the output signal of the narrow bandsubchannel would be lower than that of the wide band subchannel, forexample at a level similar to that indicated at 121 in FIG. 5. Thus, thelock out condition would occur and the solenoid would not be operated torelease the locking device. 7

If a wide frequency band generator were used which had a much greaterpower output so that sufficient energy lay within the frequency band ofthe narrow band amplifier 105 to make the output signal of the narrowband channel greater than that of the wide band channel, then it wouldbe possible to deceive the system. To avoid this problem a delay circuit123, which may consist of a capacitor, is provided in the narrow bandchannel, providing sufficient delay to ensure that in the event ofsudden saturation of both amplifiers 105 and 107 it will always be therelay 108 which operates first, thus locking out the system.

If a swept frequency generator is brought within range of the pick-up101 then the lock-out conditions illustrated by the left hand side ofFIG. 5 would be present. The locking system is prevented from releasingduring the short periods of time when the generator frequency passesthrough thepass band of the narrow band amplifier 105 because the lockout subchannel will already have locked out the output of the narrowband subchannel.

The security of the system is then further improved by the addition ofmore channels, two channels being illustrated in FIG. 2 but more thantwo channels being quite simple to arrange. The situation then is thatconcurrent closure of the series of contacts 110, 110, etc. in the powersupply circuit 111 can only be achieved if in every one of the channelsthe output of the narrow band subchannel reaches a predetermined levelbefore the output of the wide band subchannel in the same channel does.

The lock out contacts 112 or 112 can be arranged to operate some form ofalarm or warning device so as to provide an alarm or warning when anyattempt is made to release the locking system using an inductive fieldgenerator which is not the right one for that system.

The invention can also be used to control the power supply to any kindof equipment, operation of which is to be restricted. For example, cashregisters are available which depend on electric power for most, if notall, of their functions, including opening of the cash drawer. Byutilising a locking system in accordance with this invention, inconjunction with a matching key device, the contacts 110 for examplebeing arranged in the cash register power supply circuit, it will beappreciated that only a person having the right key device will be ableto operate the cash register. The attempted use of a wrong key device,or the absence of a key device, will cause the power supply to stay cutoff. The same principle is applicable, in accordance with the invention,to other equipment having a power supply of any kind, e.g. lathes,hydraulic lifts, motor cars (ignition circuit or fuel supply) and mayhave safety as well as security aspects.

It is possible for the release or trip subchannel to have a broad-bandresponse curve and for the lockout channel to have a similar responsecurve but with a notch at the tuned frequency, whereby lockout will notoccur when only tuned frequency inductive energy is received.

, A preferred frequency for the generator is between 1 and 50 KHz. Thishas been found to increase security because at such relatively lowfrequency a radio transmitter would have to have very large power and acorresponding antenna to produce sufficient inductive effect at thepick-up.

The inductive coupling elements need not be ferrite cored. Othermagnetisable material, e.g. iron laminations, could be used and, in thecase of the pick-up an open coil or a large single loop (e.g. round adoorway) could be employed. The pick-up may be provided with aconductive shield e.g. of metal foil, to keep out radio waves withoutinterfering significantly with the inductive coupling.

Where the key device has more than one frequency, separate oscillatorseach driving its own inductive coupling element and tuned to arespective frequency may be used.

The sensing circuitry can be entirely solid state instead of includingrelays as described.

The DC power supply unit 15 could be arranged to operate from a batteryinstead of from AC mains, as described.

The key device can be arranged so as to automatically switch itself onif its carrier were attacked, and the sensing circuitry can be arrangedto automatically actuate an alarm of any kind in response.

The various novel features disclosed herein are believed to constituteinventions in themselves, not only in combination with each other.

I claim:

1. A locking system comprising:

a key device, said key device comprising an inductive field generatorfor providing an inductive field; inductive pick-up means for receivingsaid inductive field from the inductive field generator;

a locking device;

a release subchannel coupled to the pick-up means and responsive to thereceipt of said inductive field by the pick-up means to release thelocking device;

the key device is self-contained and battery powered.

3. A locking system as claimed in claim 1, wherein said releasesubchannel is adapted to release said locking means only when saidpick-up means receives sufficient induced energy in a limited frequencyband; and said further subchannel is adapted to prevent release of saidlocking means when said pick-up means receives sufficient energy outsidesaid frequency band, said predetermined characteristic being the absenceof said sufficient energy outside said frequency band.

4. A locking system as claimed in claim 3, wherein the limited frequencyband of the release subchannel is provided by a tuned LC circuit, saidLC circuit being connected in the release subchannel.

5. A locking system as claimed in claim 3 comprising a plurality ofchannels each said channel including a said release subchannel and asaid further subchannel, the release subchannels having differentfrequency bands and being for releasing the locking means only when thepick-up means receives sufficient induced enmy within the bands of eachof them, and each of the further subchannels being for renderingineffective its associated release subchannel when said pick-up meansreceives sufficient energy outside the frequency band of said associatedrelease subchannel.

6. A locking system as claimed in claim 1 comprising aplurality ofchannels each said channel including a said release subchannel and asaid further subchannel, the release subchannels together beingresponsive to the receipt of said inductive field by the pickup means torelease the locking device, each of the further subchannels being forrendering ineffective its associated release subchannel when thereceived inductive field does not have a respective predeterminedcharacteristic, whereby release of the locking device by the releasesubchannels is prevented unless the received inductive field has all therespective predetermined characteristics required to prevent all thefurther subchannels rendering ineffective their associated releasesubchannels.

7. A locking system as claimed in claim 6 wherein each of saidrespective predetermined characteristics is the absence of sufficientreceived energy outside a predetermined limited frequency band.

8. A locking system as claimed in claim 1 wherein said releasesubchannel and further subchannel are continuously active whereby torespond automatically when an increasing inductive field received by thepickup means reaches a threshold level.

9. A locking system as claimed in claim 1 wherein the release andfurther subchannels each contain amplifying means the gain of which isindependently adjustable.

UNITED STATES PATENT OFFICE QERTIFICATE 0F CORRECTION Patent No.3,829,836 Dated August 13, 1974 lnventofls) Walter Wilson Hugh Clarke Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

On the title page after "Appln. No. 297,303" insert:

Foreign Application Priority Data October 14, 1971 Great Britain47868/71 January 11, 1972 Great Britain 1311/72 Signed and Sealed this Ifif Day Of August1975 [SEAL] A ties t:

RUTH C. MASON C. MARSHALL DANN K ff (ummissl'nncr nj'lare'nls andTrademarks

1. A locking system comprising: a key device, said key device comprisingan inductive field generator for providing an inductive field; inductivepick-up means for receiving said inductive field from the inductivefield generator; a locking device; a release subchannel coupled to thepick-up means and responsive to the receipt of said inductive field bythe pick-up means to release the locking device; a further subchannelcoupled to the pick-up means and responsive to the receipt of saidinductive field by the pick-up means to prevent release of the lockingdevice; said further subchannel being ineffective to produce saidpreventive response when the received inductive field has apredetermined characteristic; and means for delaying the response of therelease subchannel to a received inductive field relative to theresponse of the further subchannel to said received inductive field. 2.A locking system as claimed in claim 1, wherein the key device isself-contained and battery powered.
 3. A locking system as claimed inclaim 1, wherein said release subchannel is adapted to release saidlocking means only when said pick-up means receives sufficient inducedenergy in a limited frequency band; and said further subchannel isadapted to prevent release of said locking means when said pick-up meansreceives sufficient energy outside said frequency band, saidpredetermined characteristic being the absence of said sufficient energyoutside said frequency band.
 4. A locking system as claimed in claim 3,wherein the limited frequency band of the release subchannel is providedby a tuned LC circuit, said LC circuit being connected in the releasesubchannel.
 5. A locking system as claimed in claim 3 comprising aplurality of channels each said channel including a said releasesubchannel and a said further subchannel, the release subchannels havingdifferent frequency bands and being for releasing the locking means onlywhen the pick-up means receives sufficient induced energy within thebands of each of them, and each of the further subchannels being forrendering ineffective its associated release subchannel when saidpick-up means receives sufficient energy outside the frequency band ofsaid associated release subchannel.
 6. A locking system as claimed inclaim 1 comprising a plurality of channels each said channel including asaid release subchannel and a said further subchannel, the releasesubchannels together being responsive to the receipt of said inductivefield by the pick-up means to release the locking device, each of thefurther subchannels being for rendering ineffective its associatedrelease subchannel when the received inductive field does not have arespective predetermined characteristic, whereby release of the lockingdevice by the release subchannels is prevented unless the receivedinductive field has all the respective predetermined characteristicsrequired to prevent all the further subchannels rendering ineffectivetheir associated release subchannels.
 7. A locking system as claimed inclaim 6 wherein each of said respective predetermined characteristics isthe absence of sufficient received energy outside a predeterminedlimited frequency band.
 8. A locking system as claimed in claim 1wherein said release subchannel and further subchannel are continuouslyactive whereby to respond automatically when an increasing inductivefield received by the pick-up means reaches a threshold level.
 9. Alocking system as claimed in claim 1 wherein the release and furthersubchannels each contain amplifying means the gain of which isindependently adjustable.